Here's an example of univocalic that makes use of only the vowel e:
Seventh September. The longest one word univocalic is strengthlessness.
Also see lipogram.

CONTEST:
Imagine you are a headline writer for a newspaper back in the days
when metal type was used. You have run out of all but one of the vowels
in the large type size that is used for the headline. What univocalic can you
come up with? Email your univocalic news headlines (real or made-up) to
(words at wordsmith.org). Selected entries will be featured in the weekly
compilation AWADmail and the best entry will win an autographed
copy of my books. Deadline is Friday Oct 17, 2008.

"Most notably, [Christian Bök's] 2001 Eunoia, seven years in the making,
became Canada's bestselling poetry book ever -- an incredible feat for
such explicitly experimental writing. No comforting fluff here; in the
main portion, each chapter employs but a single vowel (e.g., "Enfettered,
these sentences repress free speech"), a univocalic constraint."
Ed Park; Crystal Method; Village Voice (New York); Dec 16, 2003.

A THOUGHT FOR TODAY:

I am not only a pacifist but a militant pacifist. I am willing to fight for peace. Nothing will end war unless the people themselves refuse to go to war. -Albert Einstein, physicist, Nobel laureate (1879-1955)